\begin{table}

    \caption{Difference-in-differences estimates of the effect of nonattainment on the implicit emissions price varying the sample period.\label{tab:emissions_length}}
    \centering
    \begin{tabular}[t]{lcccccc}
    \toprule
      & (1) & (2) & (3) & (4) & (5) & (6)\\
    \midrule
& (1) & (2) & (3) & (4) & (5) & (6) \\ \midrule %% TinyTableHeader
$\beta^p_{\eta}$ & \num{0.51}** & \num{0.50}** & \num{0.33}** & \num{0.50}** & \num{0.49}** & \num{0.48}** \\
& (\num{0.23}) & (\num{0.21}) & (\num{0.17}) & (\num{0.22}) & (\num{0.23}) & (\num{0.24}) \\
Observations & 19,005 & 28,940 & 38,890 & 49,245 & 59,610 & 70,225\\
County FE          & Yes           & Yes           & Yes           & Yes           & Yes           & Yes           \\
Year FE            & No            & No            & No            & No            & No            & No            \\
Pollutant FE       & No            & No            & No            & No            & No            & No            \\
Pollutant-Year FE  & Yes           & Yes           & Yes           & Yes           & Yes           & Yes           \\
Latest Year        & 1996          & 1997          & 1998          & 1999          & 2000          & 2001          \\
\bottomrule
%\emph{Note:} The table shows estimates for versions of equation \eqref{eq:emissions_estimating_equation}. Each coefficient can be interpreted as a semi-elasticity. Panel A reports estimates of the coefficient on nonattainment status. Panel B reports estimates of the coefficient on nonattainment status interacted with a dummy variable for each pollutant. Columns 1 and 3 only include county, year, and pollutant fixed effects; Columns 2 and 4 replace the year and pollutant fixed effects with pollutant-year fixed effects. Columns 3 and 4 convert the emissions outcome variable to the theoretically-consistent emissions intensity relative to labor costs. Robust standard errors clustered at the state level are reported in parentheses. * $p < 0.10$ , ** $p < 0.05$ , *** $p < 0.01$.
%\multicolumn{1}{l}{The coefficients are estimated using data from 1990, and from 1996 to the year listed in the Latest Year row. The 1991--1995 gap reflects years in which NEI data are not available. Robust standard errors are clustered at the state level.}\\
%\multicolumn{7}{l}{\rule{0pt}{1em}* p $<$ 0.1, ** p $<$ 0.05, *** p $<$ 0.01}\\
\end{tabular}
~\\
\begin{justify}
\emph{Note:} The coefficients are estimated using data from 1990, and from 1996 to the year listed in the Latest Year row. The 1991--1995 gap reflects years in which NEI data are not available. Robust standard errors are clustered at the state level.\\* p $<$ 0.1, ** p $<$ 0.05, *** p $<$ 0.01
\end{justify}
\end{table}

